1. Technical Field
The present invention relates to a cap assembly for a rectangular type battery and a rectangular type battery having the cap assembly, and more particularly, to a rectangular type battery having an improved sealing structure.
2. Related Art
In general, a secondary battery is capable of recharging and achieving miniaturization and large capacity. Typical secondary batteries currently being used include nickel-metal hydride (Ni-MH) batteries, lithium (Li) batteries and lithium ion (Li-ion) batteries. Secondary batteries are classified into cylindrical batteries and rectangular type batteries according to the appearance type. In a rectangular type battery, an electrode plate assembly is housed in a battery case of a rectangular solid type.
A rectangular type secondary battery has a rectangular case, an electrode plate assembly inside the case, and an electrode tab in the center portion of the electrode plate assembly and extending out from the electrode plate assembly toward a cap plate. An insulator is placed adjacent to the electrode plate assembly. The cap plate is adjacent to the insulator. A hollow gasket is placed into an orifice of the cap plate, and a pin is inserted into the gasket. The pin, gasket, cap plate, and insulator can be referred to as a cap assembly of the rectangular type secondary battery.
A cap assembly for a rectangular type secondary battery can have the following problems. First, a gasket provided to form a hermetically sealed structure is fixed by deformation of a lower end of a pin. One problem associated with the provision of the gasket is that controlling various conditions for a perfect sealing operation is not easy. Also, the use of the gasket for formation of a hermetically sealed structure and an insulator for insulation of a terminal plate increases the number of components and makes the manufacturing process complex. Further, a rise in the inner pressure of a case may cause the pin to protrude outward.